The present invention relates to a counter-ceiling comprising a suspended supporting skeleton according to the preamble of claim 1. It has been known before in connection with clean rooms, laboratories, medical rooms, and the like, to install so-called counter-ceilings consisting of a suspended supporting skeleton formed by longitudinal supporting rails and transverse supporting rails (see, for example, DE-GM 19 95 158). In the case of this known counter-ceiling, where--besides--the supporting rails and the coffers inserted between the latter consist of, or are encased by a fire-resistant material, connection elements are provided whose ends are inserted into two mutually aligned transverse supporting rails while a central portion thereof overlaps the longitudinal supporting rail crossing the two transverse supporting rails. There is no possibility of mutually bracing the supporting rails forming the supporting skeleton and the connection elements so that the longitudinal and transverse rails are permitted to turn relative to each other--a phenomenon which may occur, for example, when the individual panels are loaded differently.
It is of importance for such counter-ceilings, in particular if they are intended for use in clean rooms or for medical purposes, that they must be tight, i.e. that the transverse and longitudinal supporting rails must abut flush against each other at the crossing points. In addition, it is desired that such counter-ceilings should be suited for being walked on so that bracing means are provided in the connection area at the crossing points of the supporting rails for connecting and bracing the rails with each other.
A known counter-ceiling of this type (DE-PS 28 09 674) uses for both, the longitudinal and transverse supporting rails, an identical inverse T-shaped section consisting of a vertical web and horizontal flange extending on both sides from the bottom of the web.
In order to enable such supporting rails to be interconnected, the solid vertical web is provided with thicker portions at different heights, a first thicker portion provided in the area of transition to the horizontal basic flanges comprising a laterally open longitudinal groove while another thicker portion provided on the other, remote end of the vertical web comprises an upwardly open longitudinal groove. These longitudinal grooves, in any case the upper, upwardly open longitudinal groove provided at the end of the vertical web, serve for receiving threaded rods which extend through a transverse groove, for example in a longitudinal supporting rail, and through an additional transverse bore provided therein and are fixed in place in the transverse supporting rails by screws mounted on both sides. To this end, slots which must be accessible from above must be provided in the upper thicker portion of each of the transverse supporting rails.
In order to enable the longitudinal and transverse supporting rails abutting each other to be connected also in the lower area, fitting pins or splined pins are inserted into the lower longitudinal channels provided at this point so that the longitudinal and transverse supporting rails are secured against rotation relative to each other.
The suspension of the supporting rails is effected by additional suspension brackets exhibiting an almost closed U-shape with transverse, inwardly directed legs engaging longitudinal grooves provided on both sides of the supporting rail, every two such suspension brackets supporting two sides of a metal plate provided with a threaded hole for receiving a threaded supporting rod which is in turn fixed to the raw ceiling.
It has been further known in this connection (DE-PS 32 47 506) to provide special leaf-spring clamps for biassing resiliently the coffers resting on the horizontal flanges of each rail. These leaf-spring clamps embrace the vertical web of the T section from above, engage lateral longitudinal grooves provided in the web and bear at a certain pressure against the edges of the mounted coffers, by means of outwardly projecting resilient legs.
The known counter-ceiling, which is insofar tight and also suitable for being walked on, exhibits a complex design and may present certain problems regarding the fixation at the raw ceiling by means of leaf-spring clamps. In addition, it is a problem that at the point where a bracing effect between the transverse and the longitudinal supporting elements is needed, no screw connections, but only set pins preventing relative rotation, are provided so that there is a risk that the ceiling may yield in downward direction when being walked on.
Another problem resides in the fact that although the longitudinal and the transverse supporting rails have an identical basic shape, the transverse supporting rails have to be processed and prepared additionally in order to obtain a continuous, flush underside of the supporting skeleton and to achieve a continuous and tight supporting surface for the coffer around the whole panel. To this end, the horizontal flanges must be cut off at the ends of the transverse supporting rails over a certain length to ensure that the end face of the respective vertical web can rest flush against the side of the vertical web of a supporting rail extending perpendicularly thereto. However, it is rather difficult to carry out this work with the required precision during assembly. While it would be possible to avoid this problem by differentiating from the very beginning between longitudinal supporting rails and transverse supporting rails, this would in turn render the stock-keeping and transport operations more complex.
Now, it is the object of the present invention to provide a counter-ceiling with a suspended supporting skeleton which, while being tight and suited for being walked on, exhibits a simple structure and is easy to assemble and which does not require any additional processing of the section elements in order to prepare them for use as longitudinal or transverse supporting rails, while on the other hand the whole skeleton can be rigidly braced on all sides.